Papers by Keyword: Principal Stress Direction

Abstract: In the context of laminated composite design, the integrated stiffness of the laminate depends on the number of plies, the material and the orientation of the material in each ply. The main issue of design is the prohibitive numerical simulation cost, the early technique (DMO, discrete material optimization; BCP, Bi-value Coding Parameterization Method) consists in transforming the continuous orientation angle variables to discrete design variables as multiphase material selection problems. In this work, a set of continuous orientation angle is directly considered. More precisely, the design task is the orientation of the orthotropic material in each element of the discretization and the ratio of ply thickness. In order to reduce the computational effort, Proper Orthogonal Decomposition (POD) applied to decrease the number of design variables. The numerical results in a simple case show that the proposed method is available.

Abstract: The quantity and quality of regenerated bone strongly depends on the direction and amplitude of in vivo principal stress; therefore, in vivo stress distribution near bone implants should be optimized on the basis of the morphology of the interface between an implant and bone tissue. In this study, grooves were created on the implant surface in order to improve the surface morphology of the implant for optimizing in vivo stress distribution near the implant. The preferential alignment of the biological apatite (BAp) c-axis, which is a parameter of bone quality and controls the mechanical function of bones, is closely related to stress distribution; therefore, the direction of principal stress should be matched with the direction of the groove on the implant surface. Hip implants were prepared with grooves aligned at different angles from the surface; the grooves were located on the stem portion. These implants were inserted in a beagle femur to investigate the dependency of the quantity and quality of newly formed bone in the grooves on the groove angle. The degree of preferential alignment of the BAp c-axis of the regenerated bone in the grooves strongly depends on the angle of the groove to the principal stress vector that was estimated previously to an animal experiment. The regenerated bone forms anisotropic BAp orientation in response to the principal stress in the grooves; therefore, the direction of the grooves has to be designed on the basis of the stress distribution near the implant.